EP0131713B1 - Procédé pour la production d'hypochlorite de calcium - Google Patents

Procédé pour la production d'hypochlorite de calcium Download PDF

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Publication number
EP0131713B1
EP0131713B1 EP84105592A EP84105592A EP0131713B1 EP 0131713 B1 EP0131713 B1 EP 0131713B1 EP 84105592 A EP84105592 A EP 84105592A EP 84105592 A EP84105592 A EP 84105592A EP 0131713 B1 EP0131713 B1 EP 0131713B1
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calcium hypochlorite
slurry
crystals
basic calcium
basic
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German (de)
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EP0131713A1 (fr
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Craig Alan Foster
John Holzworth Shaffer
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Olin Corp
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Olin Corp
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B11/00—Oxides or oxyacids of halogens; Salts thereof
    • C01B11/04—Hypochlorous acid
    • C01B11/06—Hypochlorites
    • C01B11/064—Hypochlorites of alkaline-earth metals

Definitions

  • This invention relates to the manufacture of calcium hypochlorite. More particularly, this invention relates to an improved continuous process for the manufacture of calcium hypochlorite.
  • Calcium hypochlorite is a commercial bleaching and sanitizing agent used particularly in the disinfection of swimming pools.
  • Calcium hypochlorite is produced by the reaction of an aqueous slurry of a calcium compound such as lime with a chlorinating agent, for example, chlorine. The chlorination reaction is conducted until crystals of a hypochlorite product are produced.
  • Neutral calcium hypochlorite, Ca(OCI) 2 is the hypochlorite product which is most commonly sold commercially. Crystals of neutral calcium hypochlorite are, however, more difficult to separate from the accompanying mother liquor than basic calcium hypochlorites such as dibasic calcium hypochlorite. Further, after separation of the crystalline hypochlorite product, it is necessary to treat the mother liquor to recover the calcium hypochlorite values or to decompose hypochlorite ions before disposal of the solution. Mother liquors recovered during the separation of neutral calcium hyopchlorite crystals tend to have higher available chlorine contents than those recovered during the separation of basic calcium hypochlorite crystals.
  • U.S. Patent No. 1,713,669 issued to R. B. MacMullin et al. describes a process in which a lime slurry is chlorinated to precipitate calcium hypochlorite which is separated from a filtrate containing hypochlorite values. The filtrate is treated with lime to precipitate basic calcium hypochlorite which is recycled to make up additional lime slurry.
  • U.S. Patent No. 1,718,285 issued to A. George, teaches a process for reacting a sodium hypochlorite solution and lime to produce neutral calcium hypochlorite crystals in a mother liquor. Following the separation of the crystalline product, the mother liquor may be treated with lime to form a basic hypochlorite which can be used to replace an equivalent amount of lime in the next cycle of the process.
  • U.S. Patent No. 3,094,380 issued to E. A. Bruce, describes the reaction of neutral calcium hypochlorite mother liquor with lime to crystallize dibasic calcium hypochlorite. A cake of dibasic calcium hypochlorite was recovered and chlorinated to produce neutral calcium hypochlorite.
  • Japanese Patent No. 56-41805, issued April 18, 1981, to T. Murakami et al teaches a process in which hemibasic calcium hypochlorite is produced by the chlorination of a slurry of lime and/or dibasic calcium hypochlorite.
  • the slurry of hemibasic calcium hypochlorite is separated from fines and impurities in a super-decanter, settler, liquid cyclone, etc.
  • the mother liquor recovered may be treated with lime to form dibasic calcium hypochlorite and recover hypochlorite values.
  • Any dibasic calcium hypochlorite recovered is chlorinated to produce hemibasic calcium hypochlorite.
  • the process of this patent lacks controls for crystal growth.
  • Another object of the present invention is to provide a process for the production of calcium hypochlorite having reduced material and energy costs.
  • a further object of the present invention is to provide a process for the production of basic calcium hypochlorites having improved separation and production rates.
  • An additional object of the present invention is to provide a process for the production of basic calcium hypochlorite having improved crystallization.
  • the invention therefore envisages a process for producing basic calcium hypochlorite by wetting lime with an aqueous slurry of basic calcium hypochlorite crystals in a mixing zone to form an aqueous lime slurry; reacting the aqueous lime slurry with a calcium hypochlorite solution in a crystallizing zone to produce a slurry of basic calcium hypochlorite crystals; the improvement of which comprises:
  • lime and a slurry of fine crystals of a basic calcium hypochlorite are admixed in mixing zone 1 to form a lime slurry.
  • Mixing zone 1 is a mixing tank or other suitable vessel having agitation means for blending the components fed thereto.
  • the lime slurry formed in mixing zone 1 is conveyed to basic hypochlorite crystallizer 2.
  • basic hypochlorite crystallizer 2 Also fed to basic hypochlorite crystallizer 2 is an aqueous solution of calcium hypochlorite which reacts with lime to produce dibasic calcium hypochlorite in accordance with equation (1): or hemibasic calcium hypochlorite, in accordance with Equation (2): Either reaction in basic hypochlorite crystallizer 2 forms a slurry of basic calcium hypochlorite crystals. The resulting slurry is conveyed to hydrocyclone 3 which separates a slurry of fine basic calcium hypochlorite crystals from a slurry of coarse basic calcium hypochlorite crystals. The slurry of fine basic calcium hypochlorite crystals is recovered as the overflow and conveyed to mixing zone 1 to be admixed with lime as discussed above.
  • the slurry of coarse basic calcium hypochlorite recovered as the underflow in hydrocyclone 3 is conveyed to basic hypochlorite separator 4 which is a solid-liquid separating apparatus such as a filter.
  • basic hypochlorite separator 4 a moist cake of basic calcium hypochlorite is separated from a mother liquor.
  • the mother liquor is an aqueous solution of sodium chloride which contains minor amounts of calcium hypochlorite, for example, from about 3 to about 4 weight percent of Ca(OCI) 2 .
  • the mother liquor may be utilized as a bleach liquor or may be recycled to the process as described more fully below.
  • Mixing zone 5 is a mixing tank or other suitable vessel having agitation means for blending the various components fed thereto.
  • Slurry chlorinator 6 is any suitable chlorination apparatus provided with agitation means for maximum contact between chlorine and slurry. It is preferred to employ as slurry chlorinator 6 an evaporator chlorinator which utilizes the chlorination technique described in U.S. Patent No. 3,241,912, issued to Bernard H. Nicolaisen on March 22, 1966.
  • the temperature within slurry chlorinator 6 is maintained within the range from about 0° to about 35°C. and preferably from about 20° to about 30°C.
  • the primary products of slurry chlorinator 6 are neutral calcium hypochlorite, sodium chloride and water.
  • slurry chlorinator 6 it is preferred to fill slurry chlorinator 6 with a slurry or "paste" of calcium hypochlorite solids suspended in an aqueous solution of sodium chloride and calcium hypochlorite, with an excess of lime or other alkali concentration in the slurry being less than about 1.0 and preferably less than about 0.50 percent by weight.
  • the rate of feed of mixing zone slurry and chlorine to slurry chlorinator 6 and the rate of evaporation of water, if any, are adjusted to maintain the concentration of unreacted lime or other alkali during the reaction below about 1.0 percent.
  • a portion of the resulting paste produced in slurry chlorinator 6 comprised of solid neutral calcium hypochlorite dihydrate and a paste liquor, which is predominately an aqueous solution of sodium chloride and calcium hypochlorite, is continuously withdrawn from slurry chlorinator 6 and conveyed to cake separator 7.
  • Cake separator 7 is a filter, centrifuge, or other suitable solid-liquid separating apparatus capable of separating a moist cake of calcium hypochlorite dihydrate crystals from the paste liquor.
  • Moist cake from cake separator 7 generally contains from about 40 to about 60 percent by weight of calcium hypochlorite dihydrate, from about 2 to about 15 percent by weight of sodium chloride, and from about 40 to about 50 percent by weight of water. Moist cake is generally conveyed to dryer 8 where it is heated to remove most of the water. Dryer 8 is any suitable drying unit or units capable of reducing the moisture content of the calcium hypochlorite cake to the desired level without causing excessive decomposition of the calcium hypochlorite particles.
  • the underflow with coarse crystals from hydrocyclone 3 is returned to basic hypochlorite crystallizer 2.
  • a dense slurry of coarse basic calcium hypochlorite crystals containing a small portion of fine crystals is formed and conveyed from basic hypochlorite crystallizer 2 to basic hypochlorite separator 4.
  • a portion of the mother liquor recovered from basic hypochlorite separator 4 is recycled to mixing zone 1, along with the slurry of fine crystals of basic calcium hypochlorite from hydrocyclone 3, to be admixed with lime.
  • the slurry of coarse basic calcium hypochlorite crystals from hydrocyclone 3 is passed through elutriator 9 for the removal of insoluble lime impurities.
  • the elutriant is a clean filtrate produced in impurity separator 10 which discharges the insoluble impurities to solid wastes or land fill.
  • the process illustrated in Figure 4 includes the addition of a portion of the basic calcium hypochlorite cake recovered from basic hypochlorite separator 4 to mixing zone 11. Also conveyed to mixing zone 11 is the moist cake of calcium hypochlorite dihydrate recovered from cake separator 7 or, if desired, calcium hypochlorite dihydrate paste from slurry chlorinator 6. Admixture of the basic calcium hypochlorite with the calcium hypochlorite dihydrate produces a calcium hypochlorite mixture which is conveyed to dryer 8, dried and recovered as a calcium hypochlorite product having a reduced available chlorine content, for example, from about 40 to about 65 percent.
  • the primary raw materials for the process of this invention are lime, an alkali metal hypochlorite such as sodium hypochlorite, chlorine and water.
  • Lime is added to the process at mixing zone 1 and mixing zone 5.
  • relatively impure lime may be utilized to prepare a relatively pure calcium hypochlorite product.
  • lime having an active lime content as low as 85 percent by weight or less may be added to mixing zone 1 in accordance with the process of this invention and produce a relatively pure calcium hypochlorite product.
  • the active lime content of the lime fed to mixing zone 1 and mixing zone 5 ranges from about 85 to about 100 percent, and preferably from about 90 to about 97 percent by weight of active lime.
  • Lime impurities of the type described above may range from about 0 to about 15 percent and generally from about 3 to about 10 percent by weight of the lime.
  • Typical illustrative specifications for a preferred lime feed and for an acceptable lime feed are as follows:
  • the average particle size of lime fed to the process generally is substantially all -44 micron (wet screen analysis), but particles up to about -74 micron may be employed, if desired.
  • the impurity content of lime in the lime feed is greater than about 5 percent by weight, it may be desirable to employ a lime purification step, as illustrated by the processes of Figures 3 and 4, to remove impurities from at least a portion of the lime.
  • Alkali metal hypochlorites are employed as reactants in the present invention and one of the products is an alkali metal chloride.
  • the invention will be described hereinafter in terms of "sodium hypochlorite" and "sodium chloride”.
  • any other suitable alkali metal hypochlorite such as potassium hypochlorite can serve as a substitute or partial replacement for the corresponding sodium compounds.
  • one of the products will be potassium chloride.
  • the process can also be operated with a mixture of these alkali metal compounds if the efficiency of separating products is not important to the operation.
  • Sodium hypochlorite added to mixing zone 5, may be prepared by chlorinating an aqueous solution of sodium hydroxide in a suitable agitated chlorinator reactor (not shown).
  • the sodium hydroxide concentration in the aqueous solution used to make sodium hypochlorite forfeed to mixing zone 5 ranges from about 20 to about 75 and preferably from about 35 to about 55 percent by weight.
  • Chlorine is added to slurry chlorinator 6 in either gaseous or liquid form.
  • the chlorination reaction is carried out preferably in an evaporator-type chlorinator of the type described above.
  • the basic calcium hypochlorite produced in the novel process of the present invention may be dibasic calcium hypochlorite or hemibasic calcium hypochlorite. To simplify the following portions of the disclosure, the process will be described in terms of dibasic calcium hypochlorite, the preferred embodiment of basic calcium hypochlorite.
  • the lime slurry prepared preferably contains from about 10 to about 20 percent by weight of Ca(OH) 2 , and more preferably from about 12 to about 15 percent by weight of Ca(OH) 2 . Concentrations of Ca(OH) 2 higher than about 20 percent may be used, however, this may result in excessive crystal nucleation which is undesirable. At concentrations lower than about 10 percent by weight of Ca(OH) 2 , additional reactor volume may be required to maintain the desired residence reaction time.
  • Fine crystals present in the lime slurry formed serve as a seed bed for basic hypochlorite crystallizer 2 and prevent the formation of excessive nucleation sites in the crystallizer.
  • the addition of fine crystals to the lime slurry results in the production of dibasic calcium hypochlorite crystals having an increased average crystal size and also improved control of the range of dibasic calcium hypochlorite crystal sizes produced. The production of both very fine crystals and very large crystals is reduced.
  • Paste liquor from cake separator 7 generally has a sodium chloride concentration ranging from about 15 to about 22 percent, and preferably from about 17 to about 20 percent by weight; a calcium hypochlorite concentration ranging from about 7 to about 15 percent and preferably from about 8 to about 12 percent by weight; and a water content ranging from about 60 to about 75 percent, and preferably from about 68 to about 73 percent by weight.
  • paste liquor is reacted wtih a lime slurry in basic hypochlorite crystallizer 2 to produce dibasic calcium hypochlorite crystals.
  • the reaction in basic hypochlorite crystallizer 2 is carefully controlled with respect to the concentration of available chlorine and the total alkalinity.
  • basic hypochlorite crystallizer 2 is operated to maintain the oxidation-reduction potential of the dibasic calcium hypochlorite slurry in the range of from about 690 to about 705 millivolts at temperatures of 30° to 50°C. Where the oxidation-reduction potential of the reaction mixture is above about 705 millivolts the calcium hypochlorite concentration of the mother liquor recovered from dibasic separator 4 is undesirably high. At oxidation-reduction potentials below about 690 millivolts, the separation rates of the slurry of dibasic calcium hypochlorite crystals in dibasic separator are significantly reduced.
  • Total alkalinity of the reaction mixture of paste liquor and lime within basic hypochlorite crystallizer 2 is maintained within the range of from about 2 to about 6, and preferably from about 3 to about 4 percent.
  • Total alkalinity of the reaction mixture is provided by the dibasic calcium hypochlorite crystals, free lime and basic impurities present such as calcium carbonate, magnesium hydroxide, magnesium oxide, calcium oxide and the like. Where the total alkalinity is above about 6 percent, the presence of excessive amounts of free lime reduces the separation rate of the slurry in basic hypochlorite separator 4. Reduction of the total alkalinity below about 2 percent results in the formation of crystals of hemibasic calcium hypochlorite.
  • the temperature of the reaction mixture of paste liquor and lime in basic hypochlorite crystallizer 2 is maintained within the range of from about 30° to about 50°C., preferably at from about 35° to about 42°C., and more preferably at from about 40° to about 42°C.
  • Operating the basic hypochlorite crystallizer within these temperature ranges results in the growth of dibasic calcium hypochlorite crystals which are readily filtered, are stable, and where the production of fine crystals is controlled.
  • temperatures below about 30°C. are employed in the basic hypochlorite crystallizer, the crystals grqwn are very fine. At temperatures above about 45°C., the crystals are readily filtered, but the rate of decomposition increases resulting in the formation of excessive amounts of calcium chlorate.
  • the slurry of dibasic calcium hypochlorite, produced in basic hypochlorite crystallizer 2 has a solids content in the range of from about 7 to about 10 percent.
  • Hydrocyclone 3 is a non-rotary separator having a tangential inlet into which is fed that dibasic calcium hypochlorite slurry produced in basic hypochlorite crystallizer 2.
  • the slurry swirls about a vortex finder to separate by centrifugal force the coarse crystals from the fine crystals, with the coarse crystals flowing down the cone section to the apex opening from which a slurry of coarse dibasic calcium hypochlorite is removed as the underflow.
  • a slurry of fine crystals and insoluble particles present passes upwardly through the vortex finder and is removed as the overflow and conveyed to mixing zone 1.
  • the slurry of fine crystals of dibasic calcium hypochlorite recovered as the overflow from hydrocyclone 3 contains, in addition to crystals less than 50 microns in size, particles of unreacted lime and insoluble impurities. Where low grade lime sources are employed, these lime and insoluble solid particles may be removed as shown in the novel processes illustrated in Figures 3 and 4, employing, for example, an elutriator or other suitable hydraulic classifiers.
  • a portion of the fines slurry may also be recycled to basic hypochlorite crystallizer 2, if desired.
  • the slurry of coarse dibasic calcium hypochlorite crystals recovered as the underflow from hydrocyclone 3 contains crystals at least about 95 percent of which are, in the size range from 50 to 1200, and preferably from 200 to 1000 micrometers.
  • This coarse crystal slurry is preferably conveyed to basic hypochlorite separator 4, but all or a portion of the course slurry recovered from hydrocyclone 3 may be recycled to basic hypochlorite crystallizer 2 or a holding tank to provide a more dense slurry of dibasic calcium hypochlorite crystals to be fed to basic hypochlorite separator 4.
  • Dibasic calcium hypochlorite cakes recovered from basic hypochlorite separator 4 have a calcium hypochlorite content in the range of from about 20 to about 45 percent by weight; a Ca(OH) 2 content in the range of from about 20 to about 40 percent by weight; and a liquid content of from about 15 to about 35 percent by weight, where the liquid is an aqueous solution of calcium hypochlorite and sodium chloride.
  • the dibasic calcium hypochlorite cake is conveyed to mixing zone 5 and admixed with additional lime and the sodium hypochlorite solution.
  • the ultimate water content in the mixing zone slurry is controlled by adjusting the water content of the various feed streams to mixing zone 5.
  • the water used in forming the lime slurry or added directly thereto, the water content of the sodium hypochlorite solution, and the water content of the dibasic calcium hypochlorite cake from dibasic separator 4 are controlled to obtain a mixing zone slurry of the desired concentration range.
  • Slurry chlorinator 6, at start-up is preferably filled with a slurry of calcium hypochlorite solids suspended in an aqueous solution of sodium chloride.
  • the excess lime or other alkali in the slurry is maintained below about 1.0 and preferably less than about 0.5 percent by weight of the slurry.
  • the feed rate of mixing zone slurry and chlorine to slurry chlorinator 6 and the withdrawal rate of the resulting neutral calcium hypochlorite paste are adjusted to achieve substantially complete chlorination of the calcium values fed to slurry chlorinator 6 in the mixing zone slurry, while maintaining the total alkali concentration in slurry chlorinator 6 preferably below about 1.0 percent by weight of the slurry.
  • Paste from slurry chlorinator 6 is predominately a slurry of neutral calcium hypochlorite in an aqueous solution of sodium chloride and calcium hypochlorite.
  • the paste contains neutral calcium hypochlorite dihydrate crystals in the concentration of from about 10 to about 35 and preferably from about 15 to about 30 percent by weight.
  • These crystals are predominately rectangular platelets which are only a few microns in thickness, but have substantially equal sides ranging from about 50 to about 300 microns in length with the major portion having sides ranging from about 100 microns to about 250 microns in length.
  • less than about 10 percent of the crystals are "twin crystals" which entrain paste liquor, and which are both difficult to separate from the paste liquor and difficult to dry.
  • Moist cake from cake separator 7 contains from about 40 to about 60 percent by weight of Ca(OCI) 2 , from about 2 to about 15 percent by weight of NaCl, and from about 40 to about 50 percent by weight of water.
  • This moist cake may be used directly in the treatment of water systems such as swimming pools and the like, but is generally dried and stored prior to use.
  • the moist cake is dried by known means, for example, using a spray dryer, turbodryer or vacuum dryer where the appropriate temperature ranges are employed to reduce the water content to the desired level.
  • the cake is dried, for example, in a turbodryer with hot air while maintaining the product temperature in the range from about 35°C to about 110°C., and preferably from about 40° to about 95°C.
  • Dibasic mother liquor recovered from basic hypochlorite separator 4 is an aqueous solution containing sodium chloride and small amounts of dibasic calcium hypochlorite, i.e., from about 0 to about 0.75 percent by weight of Ca(OCl)2 ⁇ 2Ca(OH) 2 .
  • dibasic mother liquor may be sold as bleach liquor or used in forming the lime slurries used in the process.
  • Dibasic mother liquor may also be treated with sodium hydroxide to recover the remaining calcium values as lime.
  • the lime produced is highly active and contains above 95% Ca(OH) 2 .
  • the dilute slurry of lime produced by the reaction of sodium hydroxide with dibasic mother liquor is fed to a separator to separate a lime slurry from a sodium chloride solution containing small concentrates of sodium hypochlorite.
  • the lime slurry may be recycled to mixing zone 1 and/or mixing zone 5.
  • the sodium chloride solution, essentially free of calcium hypochlorite and calcium hydroxide can be fed as brine to electrolytic cells for the production of chlorine and alkali metal hydroxides.
  • the salt solution may also be discarded, without further treatment, to water bodies without resulting in undesired pollution.
  • the novel process of the present invention produces crystalline dibasic calcium hypochlorite slurries having high filtration rates.
  • the process provides improved crystal growth controls and effectively prevents excess nucleation in the crystallizer resulting in the reduction of material and energy costs.
  • the process of the present invention can employ low grade lime sources as insoluble impurities can be effectively isolated and removed.
  • the process may be operated batchwise or continuously although continuous operation is preferred.
  • Lime was continuously added to a mixing tank containing an aqueous salt solution containing fine crystals of dibasic calcium hypochlorite and a slurry containing about 12 percent by weight of Ca(OH) 2 was prepared.
  • the slurry was continuously fed to a crystallizing tank along with an aqueous calcium hypochlorite solution containing about 10 percent by weight of Ca(OCI) 2 .
  • the temperature in the crystallizing tank was maintained at 40°C. and the reaction mixture held in the crystallizing tank until dibasic calcium hypochlorite crystals in the range of from about 200 to about 1000 micrometres were produced as determined by microscopic examination.
  • the slurry of dibasic calcium hypochlorite crystals was continuously removed from the crystallizer and conveyed to a dibasic separator feed tank. A portion of the slurry was passed through a hydrocyclone which separated by centrifugal force a slurry of coarse dibasic crystals as the underflow and a slurry of fine crystals of dibasic calcium hypochlorite as the overflow. The slurry of fine dibasic crystals was continuously returned to the lime mixing tank to be admixed with additional portions of lime.
  • the slurry of coarse dibasic calcium hypochlorite crystals was continuously returned to a filter feed tank and admixed with dibasic slurry from the crystallizer to form a dense dibasic calcium hypochlorite slurry.
  • This dense slurry was continuously filtered to provide a cake of dibasic calcium hypochlorite and dibasic mother liquor. Filtration of the dense dibasic calcium hypochlorite slurry was at an average ratio of 870.6 liter per hour per 0.0929 m 2 of filter area and provided a cake having an average of 26 percent moisture.
  • the dibasic calcium hypochlorite cake was continuously conveyed to a mixing tank and mixed with an aqueous solution of sodium hypochlorite containing about 32 percent by weight of NaOCI, dry lime and water, where the ratio of lime to water was 1:3 parts by weight. Following admixture of thse components, the resulting slurry was conveyed to a chlorinator to which chlorine was added to produce a calcium hypochlorite dihydrate paste containing about 1 percent by weight of free alkali. Calcium hypochlorite dihydrate paste was continuously fed to a filter to separate a moist calcium hypochlorite dihydrate cake from a paste liquor.
  • Filtration of the slurry was at an average rate of 264.97 liter per hour, per 0.0929 m 2 of filter area to produce a dibasic cake having an average moisture content of 33 percent.
  • the cake of dibasic calcium hypochlorite recovered from the separator was treated in the identical manner as that of the cake of dibasic calcium hypochlorite in Example 1 to produce a dried granular calcium hypochlorite composition having a weight percent of CA(OCI) 2 of about 70 and a weight percent of moisture of about 6.
  • Example 1 The novel continuous process of Example 1, employing separation and recycle of crystals, produced dibasic calcium hypochlorite crystals having a well defined crystal size range. These crystals filtered very well at a rapid rate to produce a dry cake of dibasic calcium hypochlorite.

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Claims (10)

1. Procédé pour produire de l'hypochlorite basique de calcium en mouillant de la chaux par une suspension aqueuse de cristaux d'hypochlorite basique de calcium, dans une zone de mélangeage, pour former une suspension aqueuse de chaux; en faisant réagir la suspension aqueuse de chaux avec une solution d'hypochlorite de calcium, dans une zone de cristallisation, pour produire une suspension de cristaux d'hypochlorite basique de calcium, procédé caractérisé en ce que
a) on sépare, dans une première zone de séparation, la suspension de cristaux d'hypochlorite basique de calcium en une suspension de fins cristaux d'hypochlorite basique de calcium et en une suspension de cristaux grossiers d'hypochlorite basique de calcium, les fins cristaux d'hypochlorite basique de calcium ayant un diamètre inférieur à 50 micromètres;
b) on recycle la suspension de fins cristaux d'hypochlorite basique de calcium vers la zone de mélangeage;
c) on convoie la suspension d'hypochlorite basique de calcium grossier vers une seconde zone de séparation pour séparer les cristaux grossiers d'hypochlorite basique de calcium d'avec une liqueur-mère d'hypochlorite de calcium; et
d) on récupère les cristaux grossiers d'hypochlorite basique de calcium.
2. Procédé selon la revendication 1, dans lequel ledit hypochlorite basique de calcium est choisi parmi les ensembles consistant en de l'hypochlorite de calcium, de l'hypochlorite hémibasique de calcium et leurs mélanges.
3. Procédé selon la revendication 2, dans lequel on introduit sous pression ladite suspension de cristaux d'hypochlorite basique de calcium dans la première zone de séparation, afin de séparer sous l'effet de la force centrifuge cette suspension de cristaux d'hypochlorite basique de calcium en ladite suspension de fins cristaux d'hypochlorite basique de calcium et ladite suspension de cristaux grossiers d'hypochlorite basique de calcium.
4. Procédé selon la revendication 2, dans lequel on introduit ladite suspension de cristaux grossiers d'hypochlorite basique dans une zone d'élutriation et on la sépare d'avec une suspension d'impurétés insolubles.
5. Procédé pour produire de l'hypochlorite de calcium, qui comprend:
a) le mouillage de la chaux par une suspension aqueuse de fins cristaux d'hypochlorite basique de calcium, dans une première zone de mélangeage, pour former une suspension aqueuse de chaux;
b) la réaction de ladite suspension aqueuse de chaux avec une solution d'hypochlorite de calcium dans une zone de cristallisation pour produire une suspension de cristaux d'hypochlorite basique de calcium;
c) la séparation de ladite suspension de cristaux d'hypochlorite basique de calcium, dans une première zone de séparation, en une suspension de fins cristaux d'hypochlorite basique de calcium et en une suspension de cristaux grossiers d'hypochlorite basique de calcium, lesdits fins cristaux d'hypochlorite basique de calcium ayant moins de 50 micromètres de diamètre;
d) le recyclage de ladite suspension de fins cristaux d'hypochlorite basique de calcium vers ladite première zone de mélangeage;
e) le convoyage de ladite suspension d'hypochlorite basique de calcium grossier vers une seconde zone de séparation pour séparer les cristaux grossiers d'hypochlorite basique de calcium d'avec une liqeur-mère d'hypochlorite de calcium;
f) le mélangeage desdits cristaux grossiers d'hypochlorite basique de calcium avec de la chaux et avec un hypochlorite de métal alcalin, dans une secone zone de mélangeage, pour former une suspension alcaline mixte;
g) la réaction de ladite suspension alcaline mixte avec du chlore pour former une pâte d'hypochlorite de calcium dihydraté;
h) la séparation de ladite pâte en un gâteau d'hypochlorite de calcium dihydraté et en une liqueur de pâte;
i) l'introduction de ladite liqueur de pâte dans ladite zone de cristallisation; et
j) le séchage dudit gâteau d'hypochlorite de calciu dihydraté pour produire de l'hypochlorite de calcium granulaire.
6. Procédé selon la revendication 5, dans lequel on enlève les impuretés insolubles présentes dans ladite suspension d'hypochlorite basique de calcium grossier avant de convoyer ladite suspension d'hypochlorite basique de calcium grossier vers ladite seconde zone de séparation.
7. Procédé selon la revendication 6, dans lequel lesdits cristaux grossiers présents dans ladite suspension de cristaux grossiers d'hypàchlorite basique de calcium ont un diamètre se situant dans l'intervalle compris entre 50 et 1200 micromètres.
8. Procédé selon la revendication 7, dans lequel on mélange une partie de ladite suspension de cristaux grossiers d'hypochlorite basique de calcium avec ladite suspension de cristaux d'hypochlorite basique de calcium pour former une suspension dense de cristaux d'hypochlorite basique de calcium et l'on convoie ladite suspension dense de cristaux d'hypochlorite basique de calcium vers ladite second zone de séparation.
9. Procédé selon la revendication 8, dans lequel on introduit ladite suspension de cristaux d'hypochlorite basique de calcium, sous pression, dans ladite première zone de séparation pour séparer, sous l'effet de la force centrifuge, ladite suspension de cristaux d'hypochlorite basique de calcium en ladite suspension de fins cristaux d'hypochlorite basique de calcium et en ladite suspension de cristaux grossiers d'hypochlorite basique de calcium.
10. Procédé selon la revendication 9, dans lequel ledit hypochlorite basique de calcium est de l'hypochlorite de calcium dibasique.
EP84105592A 1983-06-15 1984-05-16 Procédé pour la production d'hypochlorite de calcium Expired EP0131713B1 (fr)

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US06/504,704 US4487751A (en) 1983-06-15 1983-06-15 Process for calcium hypochlorite

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JP (1) JPS605005A (fr)
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JP3541439B2 (ja) * 1994-07-08 2004-07-14 ソニー株式会社 信号変調方法及び装置、並びに信号復調装置及び方法
JP3769740B2 (ja) * 1995-09-26 2006-04-26 日本曹達株式会社 溶解性が制御された次亜塩素酸カルシウム組成物錠剤の製造法

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US2374835A (en) * 1940-11-14 1945-05-01 Mathieson Alkali Works Inc Method for the production of hemibasic calcium hypochlorite
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FR962242A (fr) * 1942-12-30 1950-06-07
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Also Published As

Publication number Publication date
JPH0345004B2 (fr) 1991-07-09
JPS605005A (ja) 1985-01-11
AU572141B2 (en) 1988-05-05
ZA844192B (en) 1985-01-30
CA1199472A (fr) 1986-01-21
DE3466204D1 (en) 1987-10-22
AU2798284A (en) 1984-12-20
EP0131713A1 (fr) 1985-01-23
US4487751A (en) 1984-12-11

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